The hypothesis of this new study is that it is possible to remove bone marrow stem cells from patients with leukocyte adhesion deficiency (LAD) and infect these cells with a retroviral vector which encodes the normal human cDNA for CD18. Phase I involves removal of bone marrow from patients with leukocyte adhesion deficiency followed by retroviral infection and analysis in vitro. Phase II will involve removal of bone marrow followed by reimplantation into affected patients.